Processing of ophthalmic lenses is often performed at high-volume finishing laboratories. Such finishing labs seek to maximize efficiency, increase yields, improve quality and reduce reliance on skilled technicians, often through automation of some or all of the processing steps. Finishing labs generally face a relatively large number of work orders for lens processing. As such, it is desirable that the orders are supplied to the processing equipment at optimal rates.
Generally, processing of lenses begins when an optical laboratory technician inputs the optical prescription from a work order for a pair of lenses in the laboratory's computer. The computer then provides a printout specifying information necessary for producing the required prescription. Appropriate lens blanks are selected based on this information, and the blanks are placed in a prescription tray along with the customer's eyeglass frames. The prescription tray typically remains with the lenses and frames throughout production. While various types of trays are used in the industry, most trays have a rectangular configuration with sides or corner posts having a standard height, and are stackable. The tray, along with the printout, frames and lens blanks, are then transferred to and from various processing machines, where the lenses are marked, blocked, edged and polished.
In order to maximize efficiency, it is desirable to have a supply of trays with lenses readily available for processing by a particular machine, such as an edger that cuts the lenses to a desired peripheral contour or shape. In addition, it is often desirable to stack the trays while the lenses therein await processing, or are being transported between processing stations, in order to maximize use of space in the laboratory.